This invention relates to chain brackets, and especially to trolley brackets for supporting loads in overhead conveyor systems, which brackets are connected to conveyor chains. More particularly, the invention is an improved chain or trolley bracket which is more economical to manufacture because it is stamped from sheet metal and yet includes increased chain support strength.
Trolley and other chain brackets used in overhead conveyor systems are typically subjected to many stresses and strains. In a manufacturing plant utilizing an overhead conveyor, the conveyor usually includes numerous horizontal corners as well as changes in vertical height along its length. Each trolley bracket, which is typically supported by a wheel assembly on an overhead I-beam or other type conveyor rail or the like, is joined to a conveyor chain which extends along the conveyor rail by means of one of the chain links. A typical method is to insert a pair of trolley brackets through the open center of the link in back-to-back fashion and thereafter move the brackets outwardly with a spacer and secure them with bolts or the like to hold the link in place on the brackets. Other chain brackets, such as those typically fitted between trolley brackets, are also secured to the chain in a similar fashion.
When each combination of brackets and a chain link encounters turns in the conveyor and especially vertical changes in height, the chain changes direction urging the bracket connected links through that same change in direction. This tends to cause the rigidly mounted links to "rock" on the brackets resulting in wear to or deformation of the chain and brackets.
One prior known type of trolley bracket was forged from steel or another metal. The forging method is tremendously more expensive because it is labor intensive and requires numerous forging dies. Such dies tend to wear out quickly because of extensive configurations and projections in the trolley bracket to be formed. A forged bracket also includes metal which has to be softened by heating to allow forging, is heavier than a stamped sheet metal bracket, is more expensive to heat treat for hardness after forging, and requires secondary machining before use.
Other prior trolley brackets were stamped from sheet metal. Some of these brackets included chain support surfaces which were bent out of the sheet metal itself. Such chain supports often bent and were deformed when stressed during use on a conveyor and subjected to the above "rocking" link motion. Also, some of the prior stamped trolley brackets supported the chain only with sheared edges of the stamped metal itself which increased wear on the chain.
In addition, prior known forged or stamped trolley brackets utilized the same metal for supporting the chain links as was included in the remainder of the bracket. Because the chain support areas of the bracket are subjected to a great deal more stress, load and wear than are other portions of the bracket, the chain support areas typically failed first, necessitating replacement of the entire brackets. Use of different materials in the chain support areas for hardening of the chain supports without treating or effecting the remainder of the bracket was extremely difficult or impossible. Moreover, using sufficiently wear-resistant material for the entire bracket was prohibitively expensive.
Accordingly, a need was evident for an economical chain bracket, and especially a trolley bracket for use with overhead conveyors which would be stronger and more durable in use and could include chain supports which would resist wear and deformation during use and be formed from different materials than the remainder of the bracket if desired. This invention provides a solution to the above problems. Other inventions providing other distinct, strengthened trolley brackets are disclosed in copending, commonly assigned U.S. patent applications, Ser. No. 872,244, invented by Charles C. Frost and Siegfried K. Weis and Ser. No. 872,245, now U.S. Pat. No. 4,210,238, invented by Charles C. Frost, Gerald W. Gurney and Frederick R. Sytsma, both of which were filed on even date herewith.